Prior art anti-rotation systems are described, for example, in the patent publications JP2002-54708 and JP59-19762 and DE202008001576U and use anti-rotation structures forming part of the actuator or stably connected to it.
The traditional anti-rotation systems have the following limitations:                they are highly susceptible to misalignment between the actuator and the structure where the anti-rotation is performed; in particular, in all those applications with high operational loads and continuous operating conditions, the misalignments between actuator and anti-rotation structure generate transversal loads on the actuator which can lead to a malfunction of the device, a rapid deterioration of its performance and, therefore, a low reliability of the system;        all those applications with high operational loads and continuous operating conditions require large radial and longitudinal dimensions necessary for containing an anti-rotation structure which is sufficiently robust to satisfy the load capacity and duration requirements needed by the application;        anti-rotation systems of the sliding type are traditionally used where the pressures between the contact elements and the duration requirements are substantially reduced; in applications with high operational loads and continuous operating conditions, sliding type anti-rotations systems can lead to a rapid deterioration of the performance and, therefore, to a low reliability of the system.        